Human conglutinin

ABSTRACT

Human conglutinin, polyclonal, and monoclonal antibodies raised against human conglutinin, and their uses in therapy and diagnosis are described. 
     Human conglutinin was obtained from human plasma by affinity chromatography with anti-bovine conglutinin antibody, has a relative molecular weight of 330 and 40 K unreduced and 66 K reduced as measured by SDS-PAGE, shows calcium-dependent and sugar inhibitable binding to complement-reacted immune complexes and zymosan, and immunological cross-reaction with anti-bovine conglutinin antibody.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to human conglutinin, polyclonal and monoclonalanti-conglutinin antibody raised against human conglutinin, and theiruses in therapy and diagnosis.

2. Description of Background Art

Conglutinin is the name given by Bordet and Streng(Zentr.Bakteriol.Parasitenk. Abt. 1 Orig. 49 (1909) pp. 260-276) to thecomponent in bovine serum which induce the agglutination of erythrocytescoated with antibody and complement. Conglutinin was quite extensivelystudied at the beginning of this century and later reinvestigated byCoombs et al.: "The Serology of Conglutination and its Relation toDisease"[0 (1961) Blackwell, Oxford, and Lachmann: Adv.Immunol. 6 (1967)pp. 479-527.

The activity was ascribed to a large, elongated protein molecule (Sageet al. J.Immunol. 90 (1963) pp. 347-357). More specifically, conglutininwas found to induce agglutination of erythrocytes exposing the C3degradation product, iC3b. The C3b inactivating factor (Factor I) whichsplits the α-chain of C3b was thus originally named conglutinogenactivation factor (or KAF) (Lachmann and Muller-Eberhard, J.Immunol. 100(1968) pp. 691-698). Apparently, conglutinin shows no reactivity withnative C3 or the further degraded fragments, C3dg or C3c. This has,however, lately been questioned since solid phase conglutinin in enzymelinked immunosorbent assays (ELISA) has been found to bind fluid phaseC3c and C3b as well as iC3b (Hirani et al., J.Immunol. 134 (1985) pp.1105-1109).

The physiological function of conglutinin remains hitherto unknown.Studies in bovidae have revealed that the content of conglutinin inblood decreases during infection and at parturition (Ingram D.G."Biological aspects of conglutinin and immunoconglutinins", pp. 215-228in D.A. Ingram Ed. "Biological Activities of Complement" Karger, Basel,Switzerland).

Conglutinin shows protective activity against bacterial infections asshown by Ingram D.G. (Immunology 2, 322-333, 1959 and Immunology 2,334-345, 1959) in experiments where mice could be protected by theinjection of bovine conglutinin in the form of a euglobulin precipitatefrom normal bovine serum redissolved in saline before the injection ofpathogenic bacteria. This indicates that conglutinin is of importancefor the non-specific immunity.

Conglutinin's binding of complement solubilized immune complexes hasattracted interest. Immune complex assays based on this activity arepopular and solid phase bovine conglutinin has been used to purifysoluble circulating immune complexes (Casali and Lambert,Clin.Exp.Immunol. 37 (1979) pp. 295-309).

Conglutinin may be classified as a lectin on the basis of its reactivitywith carbohydrates.

Attempts at demonstrating conglutinin in other species than the bovidaehave generally failed (Davis and Lachmann, Biochemistry 23 (1984) p.2139). However, some authors have claimed indications for the existenceof conglutinin in swine (Barta et al., J.Immunol. 105 (1970) p. 350),and in sheep (Jonas and Stankiewiecz, Veterinary Immunology andImmunopathology 5 (1983/84 p. 289).

Despite considerable efforts the only possible analogue in the human sofar described is the iC3b receptor (CR3) (Ross et al., J.Immunol. 134(1985) pp. 3307-3315), which shows no structural homology to bovineconglutinin.

By employing functional and immunochemical analysis the inventors havenow succeeded in isolating, demonstrating and characterizing humanconglutinin.

BRIEF DESCRIPTION OF THE INVENTION

Accordingly, the invention in a first aspect relates to conglutininwhich is obtained from human plasma, and has a monomer relativemolecular weight, M_(r), of 40K measured in unreduced state and 66 Kmeasured in reduced state by sodium dodecyl sulfate polyacrylamide gelelectrophoresis (SDSPAGE), shows calcium-dependent and sugar inhibitablebinding to complement-reacted immune complexes and zymosan, andimmunological cross-reaction with chicken and rabbit antibovineconglutinin antibody. Further, the conglutinin of the inventionagglutinates alexinated, glutaraldehyde-fixed sheep erythrocytes.

In a second aspect the invention relates to an antiserum or a polyclonalanti-conglutinin antibody raised against said conglutinin.

In a third aspect the invention relates to monoclonal anti-conglutininantibodies raised against said conglutinin.

In a fourth aspect the invention relates to the use of said conglutininand its antibodies in research, therapy and diagnosis.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in details in the following parts of thespecification with reference to the attached drawing whereon

FIG. 1 shows the result of an enzyme immunoassay of human and bovineconglutinin,

FIG. 2 the inhibition by various sugars of the binding of theconglutinin of the invention to alexinated immune complexes,

FIG. 3 the binding of the human conglutinin to zymosan,

FIG. 4 the SDS-PAGE profiles of unreduced human and bovine conglutinin,

FIG. 5 the relation between relative molecular weight and mobility ofboth human and bovine conglutinin, and,

FIG. 6 the results of treating conglutinin of the invention withcollagenase.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides for a novel protein, human conglutinin, which isobtainable from human plasma by affinity chromatography with anti-bovineconglutinin antibody coupled to a solid phase.

Said conglutinin is homologous to bovine conglutinin in that it shows acalcium dependent binding to complement reacted immune complexes, andzymosan. The conglutinin of the invention is further homologous tobovine conglutinin in that it shows an immunological cross reaction withboth chicken and rabbit anti-bovine conglutinin antibody. Similar tobovine conglutinin the binding of the human conglutinin to complementreacted immune complexes is inhibited with certain sugars, notablyN-acetyl-D-glucosamine but not N-acetyl-D-mannoseamine. Also like bovineconglutinin said human conglutinin binds to zymosan in the presence ofcalcium and is eluted upon addition of ethylenediaminetetraacetic acid(EDTA).

Conglutinin has interesting pharmacological properties in that it isinvolved in the immune system through its interaction with complementfactors and immune complexes.

It is therefore contemplated that human conglutinin may be used in thetreatment of disorders in humans in which the complement system isactivated, notably disorders such as infections, autoimmune diseases,and cancers.

Conglutinin may also be used extracorporally for the removal from bloodor plasma of immune complexes containing complement activation products.This may be done by perfusion of blood or plasma over conglutinincoupled to a solid phase carrier.

Conglutinin may further be used in assays for the determination ofimmune complexes containing complement activation products.

It is likely that conglutinin deficiencies will be discovered followingthe possibility of monitoring conglutinin levels in blood provided bythe present invention, and purified conglutinin may be used to alleviatesuch conditions in humans.

Human conglutinin may be used to raise antiserum or polyclonalanti-conglutinin antibodies by immunisation of a host organism withconglutinin and subsequent recovery of the polyclonal antibodies.

For the production of monoclonal antibodies anti-conglutinin antibodyproducing mammalian cells are as known in the art isolated and fusedwith myeloma cells to produce clones of cells originating from singlefused cells each producing a monoclonal antibody directed against humanconglutinin.

Such monoclonal antibodies may be used alone or in combination for thepurposes indicated below.

The anti-conglutinin antibodies thus obtained may be used in affinitychromatography for the recovery of conglutinin from human plasma, andfor the purification of conglutinin-containing immune complexes.

Anti-conglutinin antibody may further be used for monitoring conglutininlevels in blood, which will provide important information about thebiological and physiological functions of conglutinin, and, sinceconglutinin is consumed during infections, provide means for obtaininginformation about ongoing formation of immune complexes and activationof the complement system. Decreased levels of conglutinin could furtherindicate impaired capacity for bacterial clearence.

In rheumatic, inflammatory, and autoimmune diseases, etc. the activationof the complement system is of pathophysiological importance andmonitoring the conglutinin level will provide information for theevaluation of disease activity and management.

Immune complexes are currently thought to be involved in the progressionof malignant diseases, and may consume conglutinin through activation ofcomplement. Monitoring conglutinin levels in human blood may thereforebe of importance in the management of malignant diseases.

Since it has been found that conglutinin levels in blood are lowered atparturition it is also envisaged that monitoring of the conglutininlevel during pregnancy may be used to give an early warning of apathological pregnancy, abortion, or premature birth.

Anti-human conglutinin antibodies may even further be used for theextracorporeal removal from blood or plasma of conglutinin-containingimmune complexes.

The protein of the invention, human conglutinin, purified from plasma orproduced by gene technology may also be used in reconstituting theactivity in patients suffering from diseases associated with loweredconglutinin levels or cases where large amounts are needed to combat thedisease.

Human conglutinin was obtained by batch-wise affinity chromatography ofhuman plasma with anti-bovine conglutinin antibody coupled to acyanogenbromide-activated dextran gel. The beads were treated at roomtemperature with sodium dodecyl sulfate (SDS) sample buffer containingiodoacetamide, and the eluate subjected to SDS-PAGE on 5 to 20% gradientgels. The proteins were electrophoretically transferred tonitrocellulose, cut into 2 mm strips, incubated with biotinylatedanti-bovine conglutinin antibody or biotinylated normal chicken IgG, andsubsequently developed with avidin-alkaline phosphatase conjugatesubstrate, 5-bromo-4-chloroindoxyl phosphate and nitro blue tetrazolium.

Biological Characterization

The ability of human conglutinin to bind to complement reacted immunecomplexes in the presence of calcium was demonstrated in the Bio-ELISAdescribed later, the results of which are shown in FIG. 1. The wells ofa microplate were coated with rabbit IgG, either directly by incubationwith rabbit IgG, or indirectly by first coating with bovine serumalbumin (BSA) and then rabbit anti-BSA antiserum. The wells were thenreacted with complement by incubation at 37° C. with human serum. Afterwash with EDTA the wells with complement reacted immune complexes wereincubated with dilutions of human conglutinin in buffer with EDTA orbuffer with calcium. The calcium dependent binding of conglutinin wasevaluated by the subsequent application of biotinylated anti-conglutininantibody followed by enzyme coupled avidin, and measurement of theoptical density (OD) at 405 nm. The OD values were corrected forbackground values obtained from wells incubated with buffer instead ofplasma.

In FIG. 1 OD values at 405 nm of microwells coated with rabbit IgG andhuman complement incubated with two-fold dilutions of human plasmastarting at 1/30 ( and ) or bovine serum diluted 10⁻⁴ and 10⁻⁵ ( and )in the presence of Ca²⁺ ( and ) or EDTA ( and ), and assayed for humanand bovine conglutinin as indicated above, are presented. The calciumdependence of the binding of both human and bovine conglutinin tocomplement reacted immune complexes is clearly demonstrated in FIG. 1.

In this assay it has been shown that human conglutinin cross-reacts withantibody raised by the immunization of rabbits and chickens with bovineconglutinin purified from bovine serum, and vice versa that antibodyraised against human conglutinin reacts with both bovine and humanconglutinin.

It was also shown that human conglutinin, like bovine conglutinin, isinhibited in its binding to complement reacted immune complexes bycertain sugars, notably N-acetyl-D-glucosamine, but not byN-acetyl-D-mannosamine, methyl-α-D-glucopyranoside, methyl-α-D-mannosideor saccharose. L-fucose and D-mannose also gave some inhibition as shownin FIG. 2, where the results of tests in which microwells coated withnormal rabbit IgG and reacted with human serum were incubated with humanplasma diluted 1:100 in Ca²⁺ -Tween-sodium barbital buffer (VB)containing various concentrations at N-acetyl-D-glucosamine (), glucose(). N-acetyl-D-mannosamine (), L-fucose () and D-mannose (). The resultsof incubation without sugars in Ca²⁺ -Tween-VB buffer () and inEDTA-Tween-VB () are also shown.

Further, it was shown that similarly to bovine conglutinin also humanconglutinin binds to zymosan in the presence of calcium, and is elutedupon addition of EDTA, as shown in FIG. 3.

In FIG. 3 the results of a test in which heparinized freshly drawnplasma from a donor with high activity in the conglutinin assays wasincubated with zymosan in Me²⁺ (Ca 2 mM,Mg 1 mM)-VB. Suspensions werecentrifuged (1700xg, 20 min.) and the supernatant collected, andsubsequently measured in the Bio-ELISA described hereinafter at 1:60dilution.

In the figure a comparison is seen between (1) the heparinized plasma,(2) the supernatant after incubating zymosan with plasma, (3-5) thesupernatant from washing the zymosan and (6) the EDTA eluate.

Conglutinating activity with alexinated erythrocytes has not beendemonstrated in human serum. In order to show the activity in humanplasma it proved necessary to glutaraldehyde-fix the sheep erythrocytesbefore alexinating with antibody and complement. With such erythrocytesconglutinating activity may be demonstrated in human plasma with highconglutinin content as judged by the two ELISA methods, Ag-ELISA andBio-ELISA described below.

Physical-chemical Characterization

The structural relationship between bovine and human conglutinin wasdemonstrated by the induction of the production of cross-reactingantibody upon immunization. The cross-reaction was revealed in the abovebiological assay, and also in a purely immunochemical ELISA (Ag-ELISAdescribed below), where microwells coated with F(ab')₂ fragments of saidantibodies were incubated with dilutions of human plasma or serum, anddeveloped with biotin-labelled anti-conglutinin antibody and enzymecoupled avidin. Antibodies from chickens and rabbits were used invarious combinations with identical results.

SDS-PAGE

Human conglutinin purified as above was fractionated by SDS-PAGE in thepresence of 10 mM iodoacetamide and in the absence of reducing agents.

The proteins were transferred to nitrocellulose by Western blotting, anddeveloped by incubation with biotinylated antibody against bovineconglutinin and enzyme coupled avidin. The same procedure was repeatedusing bovine conglutinin. The results are presented in FIG. 4. In FIG. 4it is clearly seen that from the human conglutinin two main bands weredeveloped. The relative molecular weights (M_(r)) of these unreducedbands were 40 K and 330 K, respectively, as estimated from a standardcurve constructed using reduced and alkylated myosin, β-galactosidase,BSA, ovalbumin, and β-lactoglobulin.

From bovine conglutinin six main bands were developed indicating that itexists in polymeric forms from monomer to hexamer, whereas the two bandsfrom human conglutinin indicates the existence of a monomer and ahexamer.

In FIG. 5 the mobilities of the six main bands from bovine conglutininare plotted on semi-logarithmic scale against relative molecular weightassuming that they represent monomer, dimer, trimer, tetramer, pentamer,and hexamer, respectively. The two bands from human conglutinin showed aslightly lower mobility than the corresponding bovine bands, but have inFIG. 5 been aligned with the bovine blot to emphasize the similarity.

In FIG. 6 it is demonstrated that human conglutinin (like bovineconglutinin) is sensitive to treatment with the protease collagenase.

In FIG. 6 lane 1 representing unreduced material eluted from beadsincubated with human plasma, a major band at 330 K is seen. In lane 3the eluted material similar to in lane 1 was reduced and alkylated. Onemajor band at 66 K is seen along with two minor bands at 90 K and 45 K.

Lane 2 shows the immunochemical staining of material from collagenasetreated beads. The 330 K band seen with the unreduced beads (lane 1) hasbeen reduced and a distinct band at 240 K has appeared.

Collagenase treatment followed by reduction and alkylation gives thestaining pattern seen in lane 4. The 66 K band seen with the reduced andalkylated non-collagenase treated material (lane 3) has disappeared.

                  TABLE 1                                                         ______________________________________                                        AMINO ACID COMPOSITION*                                                       Amino Acid     Molar %                                                        ______________________________________                                        Asp            1.2                                                            Glu            1.8                                                            Ser            6.0                                                            Gly            13.0                                                           His            1.6                                                            Arg            6.9                                                            Thr            5.1                                                            Ala            3.5                                                            Pro            5.7                                                            Tyr            3.2                                                            Val            6.5                                                            Met            1.5                                                            Cys            10.1                                                           Ile            6.5                                                            Leu            18.0                                                           Phe            4.5                                                            Lys            4.8                                                            ______________________________________                                         *Data shown are for human conglutinin protein in monomeric (reduced state     form.                                                                    

MONOCLONAL ANTIBODIES

Furthermore, the human conglutinin was identified by the use ofmonoclonal antibodies. The protein was isolated from human plasma asdescribed above by affinity chromatography on Sepharose 4B coupledchicken anti-bovine conglutinin followed by SDS-PAGE and Westernblotting onto nitrocellulose. The 330 K band was localized by immunostaining strips cut from the sides of the nitrocellulose sheet, and thearea comprising the 330 K band was cut out from the sheet, homogenizedand emulsified with complete Freund's adjuvant before injection intoBalb/c mice. After booster injections spleens were taken and thelymphocytes fused with X63-Ag 8653 myeloma cells (Kearney et al., J.Immunol. 123 (1979) pp. 1548-1550). After culture and cloning hybridomaswere isolated which produce antibody reacting with the proteinidentified as human conglutinin by the use of the cross-reactingantibodies. Monoclonal antibodies thus obtained (1) reacted withcomplement coated ELISA plates which were incubated with human plasmawith a high conglutinin titer (as judged by zymosan agglutination) inthe presence of calcium ions, but not if instead of calcium ions EDTAwas present, (2) this binding in the presence of calcium was inhibitablewith N-acetyl-D-glucosamine (3) showed no reaction if serum instead ofplasma was used, (4) when coupled to Sepharose 4B they could remove fromplasma the 330 K protein with which the anti-bovine conglutinin reacts,(5) when biotinylated and used as second antibody in the Ag-ELISA belowthey identify the same human plasma as high and low in conglutinin asdoes the biotinylated anti-bovine conglutinin, (6) the 330 K band wasstained when Western blots of partially purified human conglutinin wereincubated first with the monoclonal antibodies and subsequently withenzyme-labelled rabbit anti-mouse immunoglobulin.

The fact that the monoclonal antibodies referred to above do not bind tothe human conglutinin of the invention in serum is not a positiveindication that human conglutinin is not present in serum, but indicatesthat human conglutinin present in serum must have a configurationdifferent from its configuration in plasma.

Human conglutinin may be produced as indicated above and examplifiedbelow by isolation and purification from human serum or plasma.

It is also anticipated that human conglutinin eventually may besynthesized by any method for the synthesis of polypeptides known tothose skilled in the art.

A summary of such techniques may be found in J. M. Stewart and J. D.Young, Solid Phase Peptide Synthesis, W. H. Freeman, San Francisco, 1969and J. Meienhofer, Hormonal Proteins and Peptides, Vol. 2, (1973), p.46, Academic Press, New York, for solid phase synthesis, and in E.Schroder and K. Lubke, The Peptides, Vol. 1, (1965), Academic Press, NewYork, for classical solution synthesis.

Further, it is contemplated that human conglutinin may be produced byrecombinant DNA technology.

Human conglutinin may be presented as pharmaceutical compositions andadministered to humans in analogy with known methods. Conglutinin may beadministered perorally, topically, rectally, vaginally, intraveneously,intramuscularily, intrathecally or subcutaneously at dosages in therange of from about 1 to 1000 μg/kg body weight, although a lower orhigher dosage may be administered. The required dosage will depend onthe severity of the condition of the patient, the peptide used, the modeof administration, and the duration of treatment.

The compositions may be formulated in the form of slow-release or depotpreparations.

For the purpose of parenteral administration, conglutinin is dissolvedin sterile, isotonic saline solutions, optionally in combination withphysiologically compatible, inert carriers or fillers.

ELISA for conglutinin epitopes (Ag-ELISA)

Microplates (Immunoplate II, Nunc) were incubated overnight at roomtemperature with 200 μl of F(ab')2-fragments of chicken-antibovineconglutinin at 1 μg/ml 0.1 M hydrogen carbonate buffer per well. Thewells were washed three times in Tween-phosphate buffered saline (PBS)(0.05% v/v Tween). Test material was diluted in Tween-EDTA-phosphatebuffered saline (PBS) (0.05% Tween and 10 mM EDTA) and 200 μ1 was addedin duplicate to the plate which was incubated for 2 hours at roomtemperature. The plate was washed three times in Tween-PBS and 200 μl ofbiotinylated rabbit-anti-bovine conglutinin (500 ng/ml Tween-PBS) wasadded and incubation continued overnight at 4° C. The plate was washedthree times and avidin alkaline phosphatase (2.2×10⁻² U/ml Tween-PBS)was added. After 2 hours of incubation at room temperature and wash,substrate 4-nitrophenylphosphate (PNPP) was added to the wells at 1mg/ml diethanolamine (DEA) buffer. Optical density was read at E₄₀₅(Immunoreader NJ-2000, Intermed, Nippon, Tokyo, Japan) after incubationat 37° C. in the dark. In all tests a dilution series of a conglutininpositive human plasma was included as standard. This plasma wasarbitrarily assigned a conglutinin activity of 1000 units per ml.

ELISA for biological conglutinin activity (Bio-ELISA)

Microwells were incubated overnight at room temperature with 200 μl ofnormal rabbit IgG at 10 μg/ml tris buffered saline (TBS) and washedthree times in Tween-PBS. Subsequent complement attachment was foundmore efficient when the primary IgG coating was in TBS than whenhydrogen carbonate buffer was used. Normal donor serum diluted 10 foldin Me²⁺ (2 mM Ca, 1 mM Mg) - veronal buffer (VB) (4 mM sodium barbital0.145 M NaCl) was added and complement coating proceeded for 3 hours at37° C. A low binding of conglutinin was achieved also when theserum-incubation was excluded, probably due to activation of complementin the test plasma. The wells were washed twice in Tween-EDTA-VB (VBcontaining 10 mM EDTA and 0.05% Tween) buffer and once in Me²⁺ -Tween-VBbuffer. The test samples were added at appropriate dilution in Me²⁺-Tween-VB or EDTA-Tween-VB. After incubation for 4 hours at roomtemperature the wells were washed three times. Two hundred μl ofbiotin-labelled rabbit antibovine conglutinin, (1 μg/ml Me²⁺ -Tween-VBbuffer) was added and incubated overnight at 4° C. The plates werefurther treated as described for the Ag-ELISA.

The two ELISA assays described above were used extensively in thecharacterization of the human conglutinin of the invention and theresults of their application has been referred to in the preceding partsof this specification including the drawing.

The invention will be further illustrated in the following example. Theexample is intended only for illustration and is not intended to limitthe scope ofthe invention in any way.

EXAMPLE 1 Isolation and Purification of Human Conglutinin

(1) Human blood is collected in anticoagulant (e.g. 1/10 vol. ofphosphate-buffered citrate-dextrose or EDTA).

(2) Plasma is recovered from blood selected for high conglutinin contentby centrifugation after incubation of the blood for 1/2 to 1 hour at 37°C. (The vol. of plasma is in the following referred to as "1 vol."Unless otherwise indicated the procedures are carried out at roomtemperature).

(3) Salt fractionation. Conglutinin is purified by precipitation withsalt (e.g. 1 M ammonium sulphate, or 8% sodium sulphate) or polyethyleneglycol (PEG) (e.g. PEG 6000 at 6% (w/v)). The precipitate is collectedby centrifugation (10⁴ g, 20 minutes) and washed twice with theprecipitating solution. The washed precipitate is taken up in a smallvolume (e.g. 1/20 vol.) of water or buffered saline and dialyzed againstbuffered saline (e.g. PBS or TBS).

(4) Delipidation. The dialysate is centrifuged 1 hour at 10⁵ g, 25° C.,to remove insoluble material and lipid. The efficacy of lipid removalmay be improved increasing the density of the solution beforecentrifugation, e.g. by adjusting the solution to 1M NaCl, 10% sucroseand overlaying with a small vol. of buffered saline in which the lipidwill accumulate.

Alternatively, lipid may be removed by extraction with organic solvent(e.g. Frigen, Hoechst/Behringwerke) by treatment of either the plasma orthe precipitated material.

(5) Removal of contaminating fibronectin. The molarity of NaCl isadjusted to 1M and the solution passed through a column of insolubilizedgelatin (e.g. 1/10 vol. of Sepharose-coupled gelatin). The column iswashed with further 1/10 vol. of phosphate buffered lM NaCl with 10 mMEDTA. The effluent is pooled. The effluent is dialyzed against bufferedsaline.

The affinity of conglutinin for fibronectin in isotonic saline may beexplored through purification by affinity chromatography on solid phasefibronectin.

(6) Affinity purification on solid phase carbohydrates. Theresolubilized, clarified precipitate is treated with zymosan byincubation with stirring for 1 hour with 1/10 vol. of a 50% suspensionof zymosan in PBS, 10mM CaCl₂. The zymosan is sedimented (2000 g, 20minutes) and washed 4 times with 1 vol. of PBS/CaCl₂ . The conglutininis released by resuspending the zymosan in 1/10 vol. of PBS, 10 mM EDTAand incubating (lo minutes) before removing the zymosan bycentrifugation (7000 g, 15 minutes).

The supernatant containing conglutinin is dialyzed (against PBS or TBS),and the binding to zymosan and release with EDTA is repeated.

Agarose or N-acetyl-D-glucosamine substituted agarose may be usedinstead of zymosan, in which case the purification may be carried out bycolumn chromatography.

(7) Affinity purification with anti-conglutinin antibody.Anti-conglutinin is insolubilized (e.g. by coupling to CNBr-activatedSepharose®). The partly purified conglutinin is treated with theinsolubilized anticonglutinin either batch-wise or on a column. Thematrix is washed and the conglutinin eluted by treatment with partiallydenaturing reagent (e.g. 0.lM glycine, pH 2.4; 3M KSCN; 0.1Mdiethylamine, pH 11).

(8) Gel chromatography. The conglutinin is further purified by gelchromatography (e.g. on Sephacryl®S500) in EDTA containing bufferedsaline which may in addition contain a low concentration of SDS (e.g.0.2%).

(9) Ion exchange chromatography. The purity of the conglutinin may befurther improved by ion exchange chromatography. DEAE Sepharose® andMono-Q® beads have proved useful. The conglutinin was eluted with a NaClgradient in 10 mM phosphate.

The product was characterized as indicated above, and shown to be humanconglutinin.

I claim:
 1. Human conglutinin in substantially pure form comprising aplasma protein of monomeric molecular weight of 40,000 daltons in theunreduced state and 66,000 daltons in the reduced state, and a polymericrelative molecular weight of 330,000 daltons in the unreduced state,said protein comprising in the monomeric reduced state the followingamino acid composition:

    ______________________________________                                        Amino Acid     Molar %                                                        ______________________________________                                        Asp            1.2                                                            Glu            1.8                                                            Ser            6.0                                                            Gly            13.0                                                           His            1.6                                                            Arg            6.9                                                            Thr            5.1                                                            Ala            3.5                                                            Pro            5.7                                                            Tyr            3.2                                                            Val            6.5                                                            Met            1.5                                                            Cys            10.1                                                           Ile            6.5                                                            Leu            18.0                                                           Phe            4.5                                                            Lys            4.8;                                                           ______________________________________                                    

said protein exhibiting calcium-dependent and sugar-inhiitable bindingto complement-reacted immune complexes and zymosan, said protein beingsensitive to collagenase digestion, and said protein cross-reacting withchicken and rabbit anti-bovine conglutinin antibody.